Lead for black-lead, colored, and copying pencils and the like



Feb. 13, 1940. 'R. z-UcK|-: |T 2,190,508

LEAD FOR BLACK-LEAD, COLORED; AND COPYING PENCILS AND THE LIKE Filed Jan. 27, 1959 LE; 1 '1 f 4' /'v \5 Patented Feb. 13, 1940 UNITED STATES PATENT OFFICE LEAD FOR BLACK-LEAD, COLORED, AND COPYING PENCILS AND THE LIKE Czechoslovakia Application January 27, 1939, Serial No. 253,621 In Germany May 30, 1936 1 Claim. (01. 120-83) This invention relates to a lead for black-lead, colored and copyingpencils and the like which is cemented in a cover. In the case of such leads it is desirable that their surface allows of good cementing to the cover; on the other hand the lead must slide smoothly over the paper when writing. These two requirements are dlfllcult to fulfill simultaneously as the smooth writing requires a minimum number of pores in the lead 10 whereas the cementing adheres the tighter the the lead according to the invention consists in fitting. in the outer layer of the ordinary lead composition body distributed nest-shaped inserts which contain a substance which easily liberates 25 gas. in compressing this mixed composition body to the shape of a lead in the usual manner, and in finally subjecting the lead thus obtained to a. treatment liberating the gas, which treatment may consist of a vacuum treatment, a drying 30 treatment, a heat treatment or the like. Naph thalene in powdered state may be used for example as substance easily liberating gas.

' An embodiment of the invention is illustrated by way of example in the accompanying draw- 35 ing in which- Fig. 1 shows a lead in cross-section on a considerably enlarged scale, I

Fig. 2 is a section on line 11-11 through the end of the lead shown in Fig. 1,

Fig. 3 illustrates the production of this lead in a lead press of known type,

Fig. 4 is a cross-section through the lead composition taken on line IV-IV of Fig. 3.

The lead I in Figs. 1 and 2 has in its peripheral 5 layer indiscriminately distributed nest-shaped hollow spaces 2. Some 01' these hollow spaces are located on the surface of the lead and these hollow spaces form artificial pores of difl'erent depths and diiierent diameters. In the produc- 1 tion of the lead according to the process illustrated in Figs. 3 and 4 the outermost layer 3 of the lead composition body is provided with nestshaped inserts containing a material easily liberating gas (Fig. 4). The mixed composition body thus obtained is introduced into the usual press cylinder in the shape of a lead 8. The lead' 8 thus pressed has a cross-section similar to that shown in Figs. 1 and 2, but with the diii'erence that at the points where hollow spaces are to be subsequently formed, there are for the time being insertsv oi the gas-liberating substance. These hollow spaces are only formed when the lead is subjected to a treatment causing the liberation of gas.

I claim:

A process of manufacturing leads for pencils, color-pencils, copying-pencils or the like for use in cemented cover, consisting in providing in the outermost portion of the commonly used lead- 30 composition-body inserts containing a substance easily liberating gas, in pressing to the form of a lead the lead-composition thus prepared, and in treating this lead in a suitable manner for causing the liberation of gas. a

RICHARD ziicxna'r. 

